Typically, vehicles having a heading system, such as an aircraft having an attitude and heading reference system (AHRS), must be periodically calibrated to ensure a minimization of measurement errors. The measurement errors may be due to factors such as hard iron disturbances and/or installation misalignment associated with magnetometers or other components of the heading system. Most prior art calibration methods require numerous repositioning of the vehicles for as many as eight or more different positions to come up with an approximate calibration number. The approximate calibration number is then periodically recalculated during flight of the aircraft to minimize estimation errors. None of the prior art methods known to applicant utilize theoretical magnetic field properties of the Earth, such as theoretical values for horizontal and vertical intensity of the magnetic field at the location of the positioned vehicle, such as the aircraft on the tarmac, for comparison with actual magnetometer readings at such a position. These prior art calibration methods are time-consuming and increase the complexity of the calibration procedure and, potentially, affect the accuracy of the calibrations. Examples of such prior art methods are disclosed in U.S. Pat. Nos. 7,587,277; 8,061,049; 7,891,103; 7,146,740; and 6,860,023, none of which use the theoretical magnetic components of the Earth's magnetic field, such as obtained from a web site, to calibrate the AHRS heading.
In view of the foregoing, there is a need for simplified systems and methods that can quickly and accurately calibrate and adjust a vehicle's heading system in a manner that accounts for errors resulting from hard iron disturbances, misalignment of vehicles' components, and other factors that negatively impact the heading system.